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Practice · Chemistry · 2025 syllabus · R1.2

IB Chemistry R1.2 Energy cycles in reactions: practice questions

9 exam-style questions on R1.2 Energy cycles in reactions, SL and HL, 7 marked HL: 5 multiple choice and 4 structured. Each one comes with the mark scheme, a model answer and the reasoning behind every mark. Free with your email.

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R1.2-01 · Paper 1A style · multiple choice · 1 mark · HL

Formation and combustion at once

Which equation represents both the standard enthalpy of formation of a compound and the standard enthalpy of combustion of an element? [1]

  1. H2(g) + ½O2(g) → H2O(g)
  2. CO(g) + ½O2(g) → CO2(g)
  3. C(s, graphite) + O2(g) → CO2(g)
  4. 2H2(g) + O2(g) → 2H2O(l)
Show the answer and the reasoning

Answer: C. C is correct. One mole of CO2 forms from its elements in their standard states (formation), and one mole of graphite burns completely in oxygen (combustion). A forms steam; standard combustion of hydrogen gives liquid water. B is the combustion of CO, a compound, so it is not a formation reaction. D forms two moles, and both definitions are per mole.

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The 9 questions in R1.2

  1. R1.2-01 Formation and combustion at oncePaper 1A style · multiple choice · 1 mark · HL
  2. R1.2-02 Hess’s law from combustion dataPaper 1A style · multiple choice · 1 mark · HL
  3. R1.2-03 Combining two equationsPaper 1A style · multiple choice · 1 mark
  4. R1.2-04 Electron affinity in a cyclePaper 1A style · multiple choice · 1 mark · HL
  5. R1.2-05 Exothermic steps in a cyclePaper 1A style · multiple choice · 1 mark · HL
  6. R1.2-06 Bond enthalpies for methanolPaper 2 style · structured question · 7 marks · HL
  7. R1.2-07 Hess’s law with two routesPaper 2 style · structured question · 4 marks
  8. R1.2-08 Lattice enthalpy from a cyclePaper 2 style · structured question · 4 marks · HL
  9. R1.2-09 Hydrogenating benzenePaper 2 style · structured question · 5 marks · HL

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Every Biology and Chemistry question here is original, written for practice in the style of the papers set since the 2025 syllabus, with invented data. Developed independently from the International Baccalaureate Organization, which has not endorsed it. Found a mistake? Email vytis@limeadmissions.com with the question id.